1. Field of the Invention
The present invention relates to a conveyance apparatus which causes a workpiece which is supported by a conveyor to pass through a plurality of treating processes while changing the workpiece position, and more particularly to a conveyance apparatus which is suitable for a surface treatment line such as a car body painting line in a vehicle manufacturing factory.
Also, the present invention relates to a conveyance apparatus which is preferably used in a line in which different kinds of workpieces, made of materials such as resin, metal or the like, requiring different treating conditions, are mixed.
Further, the present invention relates to a conveyance apparatus for multi-color painting. In the present invention, a floor conveyor position is defined as a workpiece position in which a workpiece is secured to a platform and is supported by resting on the conveyor, and an overhead conveyor position is defined as a workpiece position in which a workpiece is supported by hanging. In addition, a side conveyor position is a workpiece position in which a workpiece is supported approximately horizontally to a side direction of a conveyor. Also, horizontal rotation means rotation in a plane vertically intersecting the direction of travel.
2. Description of the Prior Art
In a painting line for a vehicle, there are many treating processes such as pretreatment, electrodeposition, washing, painting, and drying. A workpiece is transferred among these treating processes by a conveyor. When painting a comparatively large body of, for example, a four-wheel vehicle by dipping is required, as shown in FIG. 11A, a workpiece W which has been transferred along a floor conveyor FC located on a floor is then transferred to and suspended from an overhead conveyor HC which is arranged to move vertically relative to a painting line. In such a condition, the workpiece W is caused to pass above pretreatment and electrodeposition baths and the like, while the conveyor itself is arranged to move vertically relative to the pretreatment and electrodeposition baths and the like. In this manner, the workpiece W is moved vertically to undergo dipping treatment and then transferred again to the floor conveyor FC.
Also, in the case of electrodeposition, to obtain fine painting quality, it is known that the workpiece must be rotated in an electrodeposition paint bath to change its position to a successive variety of positions (e.g. see Japanese Patent Publication No. Hei 6-104920 and Japanese Unexamined Patent Publication No. Hei 2-111481). Japanese Patent Publication No. Hei 6-104920 also discloses that the body undergoes electrodeposition by dipping. This method is a so-called batch type processing, in which an elevator mechanism for moving the body vertically relative to a dipping treatment bath, and a rotational mechanism for rotating the body immerged in a solution are provided. Dipping is performed by a double action of an upward and downward movement and subsequent rotation.
On the other hand, when painting a comparatively small body of a two-wheel vehicle is required, as shown in FIG. 11B, all the painting processes can be performed using the overhead conveyor HC. Accordingly, it is no longer necessary to transfer the body to other positions while being painted as with the four-wheeled vehicle, but the dipping treatment still requires the vertical operation in the same manner as shown above.
In a process wherein the workpiece position must be changed to the floor conveyor position and the overhead conveyor position, if the workpiece must be transferred whenever the workpiece position is changed while being conveyed, loss of time is caused. It is therefore desired to avoid transfer of the workpiece while it is being conveyed at least in one continuous process even though the workpiece position changes. Further, in a method such as a dipping treatment of the prior art wherein a conveyance line is continuously changed vertically, the proportion of time unusable for dipping but required only for immersing the workpiece in and removing it from a bath becomes large relative to the substantial dipping time of the workpiece. Accordingly, it is desired to reduce this loss of time. Also, in the case of the overhead conveyor, there is some possibility that the painting quality deteriorates if dust and the like falling from the overhead conveyor adhere to the workpiece. It is therefore desired to realize a conveyance method that makes it difficult for such falling substances to adhere to the workpiece. It is therefore a first object of the present invention to solve the above-mentioned disadvantages.
In a painting line in which processes are carried out in the order of a pretreatment process, painting process and drying process, the treating conditions in the pretreatment process and the drying process differ according to whether the workpiece is made of resin or of metal. For this reason, the treatments have been performed by providing an exclusive line for resin workpieces and another for metal workpieces, or switching one line depending on the material handled.
In the case of providing an exclusive line relative to the above mentioned different kinds of materials, since the amount of equipment required doubles the installation space and investment could increase. In the case of switching the line depending on the material, a loss occurs because a lot of time for switching is spent for washing the apparatus (pretreatment process), control of temperature (drying process) or the like after switching. Moreover, this loss may become larger, and in order to reduce it, it is necessary to produce the workpieces in lots. However, if produced in lots, it is impossible to produce in synchronization with another department. It is a second object of the present invention to solve such disadvantages.
In electrodeposition painting of a body of vehicle, a conveyor is generally disposed above a painting bath, and a workpiece hung from and moved by the conveyor is lowered into the painting bath and is dip-treated therein (for example, see Japanese Patent Publication No. Hei 6-104920). Also, in the case where a plurality of different colors are painted by using such a painting line, methods shown in A and B of FIG. 2 are utilized.
In the method A, separate painting baths T1, T2 for two different colors (color 1 and color 2) are arranged side by side, and diverging conveyor lines B1, B2 are arranged above the painting bath, each of the diverging lines B1, B2 being connected with a main line M before and after the painting baths. A workpiece is diverted to either of the diverging lines B1 or B2 according to the required color (either the color 1 or the color 2) and is dipped into the corresponding painting bath T1 or T2. Hereinafter, this is referred to as a diverging method. The method B is so designed that the main line M of the conveyor is arranged above a single painting bath T3, and the painting bath T3 and T4 are exchanged whenever the color is to be changed to either the color 1 or the color 2. Hereinafter, this is referred to as a color replacement method.
In the above-mentioned diverging method, because the main line M is separated into the diverging lines B1, B2, the total length of the conveyance line is increased. This causes an increase in both equipment costs and installation space. In the color replacement method, much time is required to replace the painting baths and the efficiency is reduced. Accordingly, to solve such disadvantages, it is a third object of the present invention to provide a conveyance apparatus for performing selectively painting of two different colors without increasing the length of the line and replacing the painting bath.
To solve the above-noted disadvantages, a first invention provides a dipping treatment apparatus having a conveyor disposed above a treatment bath for dipping and the like and designed to cause a workpiece which is conveyed by the conveyor to be immersed in and to emerge from the treatment bath for dipping and the like, wherein the workpiece is supported above the conveyor by a carrier, and the carrier is swung above the treatment bath for dipping and the like in a plane at right angles to the direction of travel to cause the workpiece to be immersed in and emerge from the treatment bath for dipping and the like.
According to the first invention, a workpiece is conveyed in a floor conveyor position in which it is supported on a conveyor disposed above a treatment bath for dipping and the like. When the workpiece is horizontally rotated about 180xc2x0 above the treatment bath for dipping and the like, it is immersed in the treatment bath and the like. When the workpiece is further rotated about 180xc2x0, it emerges from the treatment bath for dipping and the like to return to its original floor conveyor position. Accordingly, the workpiece undergoes the dipping treatment while being rotated horizontally. Also, the dipping treatment is performed by rotating the workpiece horizontally without moving the conveyor vertically as seen in the prior art. It is therefore possible to remarkably reduce the loss of time not related to dipping, but required only for causing the workpiece to be immersed in and to emerge from the bath. As a result, the dipping treatment can be performed efficiently.
At this time, a part of the conveyor which is positioned above the treatment bath for dipping and the like may be provided with a movable section which rotates in a plane at right angles to the direction of travel, and this movable section is caused to rotate together with the carrier.
Since a part of the conveyor is arranged to rotate horizontally as a moveable section, it is possible to strengthen the moveable section and simplify the construction comparatively. Further, a rotational means for actuating the movable section can be easily housed in a hollow section of the conveyor.
Also, the conveyor positioned above the treatment bath for dipping and the like may be disposed in one level plane.
Since the conveyor is linearly arranged in the same level plane without moving it vertically, the equipment can be simplified for easy maintenance, and equipment space can also be saved.
Further, more than one treatment bath for dipping and the like may be disposed in series, and a dipping treatment is performed for each treatment bath for dipping and the like in sequence.
If there is a plurality of treatment baths for dipping and the like, these baths are arranged in series and the workpiece is rotated horizontally above each of them. Thus, the workpiece can undergo the dipping treatment for each treatment bath for dipping and the like in sequence and as a result, the distance between each treatment bath for dipping and the like can be shortened to provide compact equipment.
Furthermore, a tact conveyance method may be employed whereby the dipping treatment is performed after the carrier is stopped above the treatment bath for dipping and the like.
The tact conveyance method is employed to convey the workpiece and the dipping treatment can be performed after the carrier is stopped above the treatment bath for dipping and the like. Accordingly, the length of the treatment bath for dipping and the like can be further shortened. In the case where a plurality of treatment baths for dipping and the like is provided, such short treatment baths for dipping and the like can be positioned adjacently to provide compact dipping treatment equipment.
In a second invention of the present application, a conveyance apparatus for conveying different kinds of workpieces in a mixed condition to treating sections is provided, wherein the apparatus is provided with a corresponding exclusive treating section on each side of a conveyor for each different kind of workpiece, the workpiece on the conveyor can be horizontally rotated selectively either to the right or left side in the direction of travel of the conveyor corresponding to the treating section, and the apparatus is constituted to treat each workpiece in accordance with the treating conditions.
Since exclusive treating sections are provided relative to different kinds of workpieces on each side of the conveyor, the workpiece on the conveyor is swung to either the right or left side according to the treating conditions, and an appropriate treatment can be performed at a treatment section suitable for this workpiece. For this reason, since it is unnecessary to provide exclusive lines for workpieces differing in required treatment conditions, depending on the material or the like, which can be produced in a common line, it is possible to save installation space and investment. Also, since it is not necessary to provide a line to be switched to produce each different kind of workpiece and it is possible to continuously transfer the different kinds of workpieces, no switching loss occurs, and since production by lots is not necessary, the production in this department can be synchronized with productions another department.
At this time, said treatment may be a pretreatment process preceding a painting process in a painting line.
In the case of a pretreatment process in a painting line, the treatment differs depending on whether the workpiece is resin or metal, but even in this case, it is possible to transfer workpieces of different materials in a mixed condition, and thereafter, since painting can be performed in a common line, the painting line can be compact.
Also, said treatment may be a drying process subsequent to a painting process in a painting line.
In a drying process subsequent to painting, also, the drying temperature differs for resin workpieces and metal workpieces. However, since the resin or the metal workpieces which have different treating temperatures can be transferred in a mixed condition, a single line can be utilized after painting, so that it is possible to have a simple painting line.
Further, said treating section comprises dipping baths, and the adjoining baths may be arranged at different heights.
In the case where the dipping treatment is performed by providing two dipping baths as an exclusive treatment section, since adjoining dipping baths have been arranged differently by height, the treatment section applied after the dipping treatment can essentially be prevented from mixing into the adjoining dipping bath.
Furthermore, in a conveyance apparatus for conveying different kinds of workpieces in a mixed condition to treating sections, said apparatus may be provided with a corresponding exclusive treating section on each side of a conveyor for each different kind of workpiece, and the apparatus is adapted to allow the workpiece on the conveyor to be horizontally rotated selectively to the right or left side in the direction of travel, corresponding to the treating conditions so as to treat the workpiece at any of the right and left exclusive treating sections or to pass the workpiece without rotating horizontally in the case where the treating condition is not suitable for any of these exclusive treating sections.
In addition to selection of right and left treating sections, a workpiece for which the treating conditions in either the right or left exclusive treating section are not suitable is allowed to pass by canceling the treatment. Therefore, the three kinds of workpieces can be handled, that is, two kinds corresponding to the right and left exclusive treating sections and one kind other than these, and it is possible to increase the number of kinds of different workpieces which can be treated simultaneously.
In a third invention, the apparatus is provided with painting sections for applying different colors at both the left and right sides of a single conveyor, and a workpiece which is guided and moved by said conveyor is allowed to rotate horizontally either to the right or left side and is painted with a required color in any one of said painting sections. At this time, it is possible to perform the painting as electrodeposition, and to provide the painting section as a dip painting bath. Further, the painting section in the present invention is a painting bath in the dipping treatment, such as the electrodeposition or the like, and can be a booth in either a spray method or a brushing method.
According to the present invention, when the workpiece being carried and guided by the conveyor reaches the painting section, the workpiece rotates horizontally in either the left or right direction and enters any of the painting sections which are arranged with the conveyor positioned therebetween and which utlilize different colors for painting, whereby the workpiece is painted with the required color in that painting section. Accordingly, painting with a different color can be performed selectively according to the direction of horizontal rotation of the workpiece. In this manner, the conveyor can be common even if the different colors are used, and since the apparatus does not require an exclusive diverging line, both the installation cost and the investment can be reduced. Also, since it is not necessary to replace the color (to replace the bath) and it is possible to transfer the workpiece continuously, the painting efficiency is outstandingly improved.
Also, if the painting method is electrodeposition, dipping baths containing different colors are provided at the left and right sides of the conveyor, and the workpiece transported to this portion of the painting bath is rotated horizontally to swing to either the left or the right. Therefore, multi-color painting can be performed efficiently by using electrodeposition.